1. Field of the Invention
This invention relates to mechanical devices containing a plurality of rigid elements wherein a centrally-acting elastic containing means causes compaction and mutual constraint among the elements, allowing the existence of a number of possible, stable configurations of the elements. Alteration of force and direction of force upon the centrally-acting elastic containing means can overcome an energy barrier and result in a rearrangement of the elements from one stable configuration into another.
2. Statement of the Prior Art
Osborne Reynolds first described volumetric dilatancy in Reynolds, O., "On the Dilatancy of Media Composed of Rigid Particles in Contact" Philosophical Magazine, 20 (S5), pp. 469-481, December 1885. In this article Reynolds describes the enclosing of a mass of solid particles or balls inside an elastic, closed envelope (latex balloon). Volumetric dilatancy is the tendency of a granular medium to expand upon shear. It has more recently been called a "locking solid". This behavior can be most easily understood by the change that occurs when the plastic envelope of a vacuum-packed package of coffee is pierced. What was a solid, hard block of compressed coffee granules suddenly becomes a loose, pliable bag of free flowing granules.
Subsequently, Reynolds developed a theory of the structure of space, gravity, and electro-magnetism in which volumetric dilatancy played an essential part: Reynolds, O., Papers on Mechanical and Physical Subjects, Vol. III, The Submechanics of the Universe, Cambridge: at the University Press, 1903. and Reynolds, O., On an Inversion of Ideas as to the Structure of the Universe (The Rede Lecture, Jun. 10, 1902), Cambridge: at the University Press, 1903. In these documents, among much else, Reynolds explains light waves as transverse vibrations in a mechanical, granular medium (or aether) caused by "reversions of complex inequalities", i.e., by a snapping back of grains into close packing, an action which is made audible and tactual in the subject invention.
The previously described volumetric dilatant devices of Reynolds, while capable of producing a locking solid, use a plurality of uniform, near-spherical grains, not rods nor disks as taught herein. In addition, herein, the visibility of the ends of the elements allows changes in their relative positions and groupings to be seen.
Examples of patents teaching compact bundle formation of elongated elements are found in U.S. Pat. No. 3,956,982 to Hill and Wynn, issued May 18, 1976 and U.S. Pat. No. 4,174,662 to Klusmier, issued Nov. 20, 1979. These patents describe devices to facilitate the assembly and fastening of bundles into a stable, unchanging configuration and do not deal with the dynamic and geometric properties of rearrangements of elements within the bundle as in the subject invention.
A theoretical physics approach is taken to mathematically describing arrangements of compacted finite systems of rigid elements in Stillinger, F. H. Jr. and Salzburg, Z. W., "Limiting Polytopc Geometry for Rigid Rods, Disks, and Spheres", pp. 179-225, Journal of Statistical Physics, Vol. 1, No. 1, 1969. A polytope is the "limiting high-compression region" of a finite system of rods, disks or spheres. The subject invention provides a method for physically modeling and visually and tactually exploring the theoretical results for the 2-dimensional rod and disk examples of Stillinger and Salzburg; but is in no way disclosed by their article.
It is believed that the subject invention is a novel way of implementing a multi-stable mechanical device with minimal means, inexpensively and effectively.